ci(code-coverage): move push:main trigger to merge_group - #810
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vikrantpuppala merged 1 commit intoMay 27, 2026
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Running the coverage suite on push:main is observational — by the time it fires, the merge has already happened and a failure can't block anything. Moving the same trigger to merge_group runs the suite against the queue's transient branch (current main + the queued PR diff, freshly merged), which is the same state push:main would have tested, but where a failure can actually eject the PR from the queue before it damages main. pull_request stays as-is so the PR author still gets fast feedback while iterating; the queue run is the gate. Not making this a required status check in the same PR — the suite takes ~17 min and would add that to every queue merge, even for PRs that don't touch driver code. Promote to required later if main breakages slip past the merge_group run without it being mandatory. The coverage override (SKIP_COVERAGE_CHECK in PR body) intentionally doesn't apply to merge_group runs — the override is an author-time escape hatch, not a queue-time bypass. github.event.pull_request.body resolves to empty under merge_group, which naturally degrades to "no override" without code changes. Co-authored-by: Isaac Signed-off-by: Vikrant Puppala <vikrant.puppala@databricks.com>
vikrantpuppala
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May 27, 2026 10:37
madhav-db
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May 27, 2026
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This was referenced May 27, 2026
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Summary
Replaces the push: main trigger on code-coverage.yml with merge_group. pull_request and workflow_dispatch stay as-is.
Why
Today the suite runs twice per PR-to-main lifecycle:
Run #2 is observational — by the time it fires, the merge is done. A failure can't block anything; it can only tell you "main is broken, go fix it." That's not protection; that's an alert.
merge_group fires while the queue is processing the PR (against a transient branch = current main + the queued PR diff, freshly merged). Same SHA-equivalent state that push:main would have tested, but a failure here actually ejects the PR from the queue before it damages main.
The principle (from this morning's audit):
This PR moves the workflow from the third category back into the second.
Why this PR doesn't also make it required
The suite takes ~17 min and would be added to every queue merge, including PRs that don't touch driver code. Queue throughput would drop materially. The right move is:
The current setup is: queue runs the suite, you see the result, but it's not gating. Strictly better than today (where the result lands after the merge), without adding queue-time cost.
Subtlety: coverage override
The SKIP_COVERAGE_CHECK PR-body override only applies under pull_request events (where github.event.pull_request.body is populated). Under merge_group, the variable resolves to empty, the grep returns no match, and the threshold is enforced. That's intentional — overrides are an author-time escape hatch, not a queue-time bypass. Documented inline.
Test plan
This pull request and its description were written by Isaac.